@misc{cryptoeprint:2009:128,
author = {Lu Xiao and Gregory G. Rose},
title = {Attacks on a Lightweight Cipher Based on a Multiple Recursive Generator},
howpublished = {Cryptology ePrint Archive, Report 2009/128},
year = {2009},
note = {\url{http://eprint.iacr.org/}},
}
You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.